This invention relates to vehicle alignment testing equipment, and more particularly to apparatus for checking sideslip.
As a vehicle, such as an automobile, rolls down the road, there should not be any lateral forces on the tires. When lateral forces are present, the not effect is the same as if the wheels were being dragged sideways as they roll down the road. Sideslip is a measure of the magnitude of these lateral forces. It is measured in units of feet/mile or meters/kilometer. For example, a sideslip measurement of twenty feet/mile means that if that vehicle were driven in a straight line for one mile, the tires would have been scuffed sideways a distance of twenty feet.
The largest influence on the sideslip measurement is total toe. As a result, a positive sideslip measurement generally reflects a toe-in condition and a negative sideslip measurement generally reflects a toe-out condition. Measuring sideslip, therefore, can quickly give the user an indication of alignment problems which should be checked further, particularly total toe.
Sideslip meters are known, but they could be improved. It is preferable that operation of sideslip meters be as automatic as possible, yet some units require that the user operate the controls several times during the process of measuring sideslip In this regard, it should be noted that sideslip is preferably a one-person test. The user should be able to set the machine, drive the vehicle under test over the meter, and then return to the meter to obtain the results.
Sideslip readings are subject to various parameters of the test, such as vehicle velocity and vehicle direction. Velocities which are too high or too low result in inaccurate sideslip readings. Similarly, sideslip measurements taken in the forward direction (front wheels of the vehicle passing over the meter first) generally differ (sometimes significantly) from measurements taken on the same vehicle traveling in the reverse direction.
Currently available meters are not believed to inform the user that the vehicle velocity was too fast or too slow. Instead, the meter simply gives the user an inaccurate reading, with no warning that the reading is inaccurate. Even if the currently available sideslip meters had some provision for informing the user of an inaccurate reading, they could still be improved. The user still might not know until he or she gets out of the vehicle and walks over to the control panel that the test was invalid because one of the parameters was not satisfied. The user would then have to walk back to the vehicle, and perform the test over again. This could happen several times It. would be preferable if the user could be informed, while still in the vehicle, that the test was unsuccessful.
Sideslip meters are generally used in an environment, the service bay, which is relatively hostile and often limited in space. It is preferred, therefore, that the meter be durable and as small as possible.